faixa piritosa ibérica, uma região mineira europeia com...

Faixa Piritosa Ibérica, uma região mineira europeia com elevado potencial para jazigos de metais básicos

João Xavier MatosLNEG/Laboratório de Geologia e Minas – UI.Recursos Minerais e Geofísica, [email protected]

Workshop Iniciativa Matérias Primas: Indústria Extractiva - Évora 2009

IberianPyriteBelt

An important European Mining Region

IPB is a world famous metallogenic base metal province characterised by giant massive sulphide deposits (>200Mt) associated with a Volcano-Sedimentary Complex of Upper Palaeozoic age (350 M years).

IPB is shared by the Portuguese Alentejo and Spanish Andalusia regions, where 90 massive sulphide deposits are know, some unexploited, some of them intensely mined since Roman times.

Presently the Neves Corvo mine (Castro Verde) is the biggest extractive project, producing Cu (Zn, Sn) concentrates (~2,2Mt/year). Aljustrel minerestarted the activity in 2008, exploiting Moinho and Feitais Zn ores (~1,8Mt/year).

Most of the IPB old mines are abandoned and present negative environmental impacts.

Rehabilitation projects are in development at Aljustrel mine by EDM.

The Iberian Pyrite Belt:

“IBERIAN PYRITE BELT,NEW SUSTAINABLE DEVELOPMENT POLICY IN THE

EUROPEAN COMMUNITY”

• The presence of active mining is an important factor for exploration.

• Green mine projects (e.g. Neves Corvo) shows the compatibility

between ore exploitation and nature protection.

• LNEG regional office improves exploration companies to a direct

contact with the complex IPB geology (best areas for research and

exploration, exploration methodologies, etc).

• Old mining projects have important negative environmental impacts.

• The improvement of the geological knowledge would be reflected in a

more sustainable exploration models and methodologies.

• Mining and geological heritage programs are important to mining site

rehabilitation

Matos & Martins 2006

Iberian Pyrite BeltIberian Pyrite Belt(Oliveira 1990, Barriga et al. 1997, Carvalho et al. & Leistel et al. 1998, Matos et al. 2000, 2004, 2006)

Massive sulphides deposits:Giant (>200Mt): Neves Corvo, AljustrelMedium deposits (5-50Mt): Lousal, S. Domingos, Caveira and Lagoa Salgada.Minor deposits (<5Mt): Salgadinho, Montinho, Chança.

Fe – Mn oxides, carbonates and silicates - stratiform and veins:nearly 100 abandoned mines, e.g. Cercal, Ferragudo, Balança, Lagoas do Paço.

Cu, Pb, Sb vein structures:tens of abandoned mines e.g. Juliana, Torgal, Barrigão, Brancanes, Ferrarias, Furnazinhas(Cu), Castro Verde (Pb), Cortes Pereiras (Sb).

IberianPyriteBelt

N

15km

Baixo Alentejo Flysch Group (Upper Visean-Moscovian)

Volcano-Sedimentary Complex (Upper Famennian-Upper Visean)Phyllite-Quartzite Group (Middle-Upper Devonian)

1 cm

Iberian Pyrite Belt: ore types VeinsVeins

Late- Variscan to Eo- Alpine mineralized faults

Vein type structures, up to 250000t (very small dimension)

Tree main systems: Cu, PbCu, Pb--Ba, Sb (Au)Ba, Sb (Au) + quartz + carbonates

Examples: Barrigão, Ferrarias, Fortes, Brancanes, Porteirinhos, Cortes Pereiras

Exploited in the XIX century, evaluated in the 1930’s and 1950’s

Associated with the Flysch Group and VS Complex, sparse distribution

Ferrarias CM1 borehole, tectonic breccia + chalcopyrite and carbonates, Matos et al. 2003

Iberian Pyrite Belt: ore types Manganese and iron oxidesManganese and iron oxides

Related with Volcano Sedimentary Complex jaspers horizons

Stratiform and vein type structures, (small to medium dimension)

Barite as sub-product at Cercal Rosalgar mines

Examples: Cercal, Ferragudo, Balança, Aljustrel (Feitais, Mangancha)

Exploited in the XIX century,until 2001 in Portugal

Cercal mine, Matos e Rosa 2001

Iberian Pyrite Belt: ore types Massive sulphidesMassive sulphides

Volcanogenic hosted massive sulphides, associated with the Volcano Sedimentary Complex hydrothermal submarine activity

Type of occurrence (stratiform and singenetic): exhalative massive sulphides; shallow

subsurface replacement of muds/shales or coherent felsic volcanics

Pyrite is the main sulphide (> 90 % of the total sulphide minerals). Locally significant amounts of sphalerite, galena and chalcopyrite can occur.

Neves Corvo ore (Photo F. Barriga) Algares gossan (massive sulphide oxidation)

IBERIANPYRITE BELT

The Mining Life Cycle in the province:

2009 AC2009 AC

90 massive sulphide deposits

>2500Mt Py

Matos et al. 2008

Exploration Mining Re-Mining Post-Mining Abandoned

Mining Life Cycle…

Neves Corvo

Las Cruces

Aljustrel

Aguas Teñidas

La Zarza

Cerro Colorado

São Domingos

Lousal

Caveira

Chança

Peña de Hierro

Tharsis

Rio Tinto

Montinho

Mn mines

Cu mines

San Miguel

Others…

Lagoa Salgada

Salgadinho

Las Majadas

Castielejitos

Definition of geo- eco- mining routes. Heritage promotion by

websites, newsletters, papers, books, maps

Technical support to current IPB museums

– e.g. São Domingos, Aljustrel and Lousal mines;

Development of a transnational network of

IPB mining sites, regions:

Alentejo Huelva (Andalusia)Algarve Mancomunidad Cuenca Minera

Mancomunidad Andevalo Minero

Objectives:RUMYS

Iberian Pyrite Belt

PyriteRoute

“5000 YearsOf Mining”

Iberian Iberian Pyrite BeltPyrite Belt

· 5000 Years of Mining ·

Portuguese Geological Survey team at Lagoa Salgada LS3 borehole (1992)

ExploringIPB…Portuguese Geological Survey

Companies:SomincorLundin, AGC, Redcorp, Iberian Resources,Northern Lyon, Maepa,Amax, Asarco, Billiton, BP, BRGM, Conasa,EDM, ELF, EMSC, Lea Cross, MEI, Minaport, Mason,Portuglobal, Redfern, SPE,SEREM, SMS, Peñarroya, Rio Tinto, SMRA, Utah

Exploring the IPBPortuguese Sector

Geologykeyguides

Mining areas – detail research around know deposits

Hydrothermal alteration – chlorite, silica, sericite

Sulphide remobilization –veins, fissural/stockworks

Felsic volcanics – breccia zones, proximal facies

Black shales – disseminated ore, veins

Cherts, jaspers, barite

Fault zones, shear zones

Horsts and grabens


Exploration tools

Exploration permit/

Objectives

Exploration permit/

Objectives

Target selectionTarget selectionGeophysics

GeochemistryGeology

GeophysicsGeochemistry

Geology

Area evaluation

Area evaluation

AbandonAbandon

Detail studyDetail study

Drill program

Drill program


Metho-dology

New projectNew project

Reserves measurement

Reserves measurement

FeasibilityFeasibility

Ore deposit characterization,

metalogeneticmodel

Ore deposit characterization,

metalogeneticmodel

Mine!

IPB geological heritage at LNEG:>200km exploration boreholes at Aparis, Aljustrel, S. Luís, Alfragide sites - estimated value 20M20M€€!!

Ossa Morena Aparis (Barrancos) copper mine in the 1950´s

A new drill store project (1000km) is being study by LNEG.The infrastructure will be integrated in the newCEGMA – Centro de Estudos Geológicos e Mineiros do AlentejoA regional technical and research unit

Iberian Pyrite Belt exploration boreholes:22 holes > 1000 m depth (maximum 1888m)37 holes 800m – 1000m depth


Residual gravimetry

Ad. BobCarmichael2006

Somincor/Lundin

ENMR WorkshopAljustrel

Exploration potential – Neves Corvo extension

ZAMBUJAL

LOMBADOR

NEVES

CORVO

GRA¦A

C850GP2

C850GP1C870G

P1

S940GP1

N870GP2

C590

GP2

C590G P4

C590G P3

C700GP1

N700G P5

N870GP3

N700

GP8

N700

GP

7

200 4

2004

C720GP

N900GP1

S940GP1

2004

2004

CT01

Th K U Total countSMRA AIRBORNE SURVEY (1991)

Magnetic field

Working without geological models…(IPB Exploration Companies Final Reports, LNEG Archives)


Investments

Source: DGEG2006

Exploring the IPB Portuguese Sector

~800 Boreholes:304km30M€>1400m(7)1400-1000m(15)1000-800m(37)800-600m(94)600-400m(175)<400m(471)

Matos 2009LNEG

1965 1965 -- 20082008Estação (SFM)

Gavião (SMS)Salgadinho (SFM)

Neves Corvo (SMS/SEREM/SMMPA)Lombador (Somincor)

Lagoa Salgada (SFM)


~800 Boreholes:304km30M€>1400m(7)1400-1000m(15)1000-800m(37)800-600m(94)600-400m(175)<400m(471)

Matos 2009LNEG

1965 1965 -- 20082008

Chanoca

Boreholes > 1000m length: Somincor (21), Billiton (1)Neves Corvo Lombador mining boreholes not included

Cotovio (1888m)> 600m, after Neves Corvo

> 1000m, Neves Corvo area

Deep targets: gravimetry+seismic+magneto-telluric


~800 Boreholes:Area distribution>1400m(7)1400-1000m(15)1000-800m(37)800-600m(94)600-400m(175)<400m(471)

Matos 2009LNEG

IPBIPB

São Domingos open pit mapping and stratigraphic columnsMatos et al. 2006, Oliveira et al. 2006, Pereira et al. 2006, 2007, 2008

North branchNorth branch

IPB Stratigraphic columns Oliveira et al. 2006, Pereira et al. 2006, 2007, 2008

South branchSouth branch

Iberian Iberian Pyrite BeltPyrite Belt

· 5000 Years of Mining ·

Development of 3D exploration geological and geophysical models at regional and local scale, using geological mapping, bore-hole data, gravimetric, magnetic, radiometric and electric-magnetic data. Development of remote sensing studies;

Paleontological and stratigraphic study of geological units to identify favourable age horizons;

Detail study of each deposit focus on hydrothermal alteration and ore geological history favourable to metal enrichment (e.g. tectonicdeformation, metal zoning, supergene alteration);

Ore metal research (e.g. Au, Ag, In, Se, Co);

Data integration using GIS database systems;

Build the IPB Alentejo Region Research Centre -CEGMA

Conclusions – Iberian Pyrite Belt new goals:

faixa piritosa ibérica, uma região mineira europeia com...

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